title: Review article: 'true' re-infection of Helicobacter pylori after successful eradication--worldwide annual rates, risk factors and clinical implications.
abstract: BACKGROUND
  The incidence of 'true' re-infection with Helicobacter pylori after successful eradication remains uncertain.
  
  
  OBJECTIVE
  To determine the worldwide rates, risk factors and clinical implications of 'true' re-infection of Helicobacter pylori. 'True' re-infection of H. pylori is defined as the situation where tests for H. pylori infection, which were negative for 12 months after eradication, become positive again at a later stage.
  
  
  RESULTS
  Thirty six studies were identified through a literature search to be able to produce annual rates of 'true' re-infection, and data from 33 original articles were considered reliable and adequate in the further review. Generally, the reported rates varied from 0% to 23.4% in adults and from 1.9% to 9.6% in children. Most studies from developed countries reported rates of less than 1%, whereas relatively higher rates were reported in most of the developing countries. Small sample sizes included in the studies appeared to be associated with increased re-infection rates. Interfamilial transmission is the major cause of re-infection, although iatrogenic re-infection through contaminated endoscopic equipment has been reported.
  
  
  CONCLUSIONS
  Helicobacter pylori re-infection is not a concern in a clinical setting, especially in the developed world; however, caution must be exercised in most developing countries.
authors.affiliation: Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China.
authors.forename: Y-Y
authors.initials: YY
authors.lastname: Zhang
authors.forename: H H-X
authors.initials: HH
authors.lastname: Xia
authors.forename: Z-H
authors.initials: ZH
authors.lastname: Zhuang
authors.forename: J
authors.initials: J
authors.lastname: Zhong
mesh_terms: D000328:Adult; D002648:Child; D019049:Developed Countries; D003906:Developing Countries; D016481:Helicobacter Infections / Q000150:complications / Q000453:epidemiology*; D016480:Helicobacter pylori; D006801:Humans; D012008:Recurrence; D012307:Risk Factors; D013997:Time Factors